From: Johannes Berg <johannes.berg@intel.com> stable inclusion from stable-v5.10.121 commit 7f8fd5dd43cd7306bb8fc519c13bcf1df7de3783 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 57ae0b67b747031bc41fb44643aa5344ab58607e upstream. The previous fix here was only partially correct, it did result in returning a proper error value in case of error, but it also clobbered the pid that we need to return from this function (not just zero for success). As a result, it returned 0 here, but later this is treated as a pid and used to kill the process, but since it's now 0 we kill(0, SIGKILL), which makes UML kill itself rather than just the helper thread. Fix that and make it more obvious by using a separate variable for the pid. Fixes: ccf1236ecac4 ("um: fix error return code in winch_tramp()") Reported-and-tested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Cc: stable@vger.kernel.org Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Acked-by: Xie XiuQi <xiexiuqi@huawei.com> --- arch/um/drivers/chan_user.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c index 6040817c036f..25727ed648b7 100644 --- a/arch/um/drivers/chan_user.c +++ b/arch/um/drivers/chan_user.c @@ -220,7 +220,7 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out, unsigned long *stack_out) { struct winch_data data; - int fds[2], n, err; + int fds[2], n, err, pid; char c; err = os_pipe(fds, 1, 1); @@ -238,8 +238,9 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out, * problem with /dev/net/tun, which if held open by this * thread, prevents the TUN/TAP device from being reused. */ - err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out); - if (err < 0) { + pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out); + if (pid < 0) { + err = pid; printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n", -err); goto out_close; @@ -263,7 +264,7 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out, goto out_close; } - return err; + return pid; out_close: close(fds[1]); -- 2.20.1